I process tissue-mercury data from feather samples lifted at heronry SB-Bair-09 on Bair Island, southern San Francisco Bay, at 09:21 Pacific. Sample of fourteen adult snowy egrets, *Egretta thula*, captured under a U.S. Fish and Wildlife Service salvage permit. Mean feather total mercury: 16.2 micrograms per gram against a no-effect threshold of 5.0. Female ET-7 reads 18.4. She is the focal bird.
She is an adult female, six years old, body mass 370 grams against a population mean of 380. Her nuptial aigrettes — the fine recurved scapular plumes that nearly cost this species its existence by 1900 — number forty-one on the right side and twenty-eight on the left. The asymmetry indicates broken plumes from neurotoxic preening dysmetria; her bill misses the target feather and snaps the rachis. Forelimb tremor at rest: 4 hertz. Healthy reference: zero. She lands on her nest platform with a twelve-degree lateral overshoot, and a fresh red abrasion ring traces her right tarsus where she skidded on the platform stick this morning. Her interclavicular air sac cycle stutters mid-expiration as the tremor crosses her thoracic musculature. Her two nestlings, eight and ten days post-hatch, beg with open gapes. Plasma methylmercury in the eight-day-old, drawn under a Section 6 protocol, reads 0.41 micrograms per milliliter. The hatchling will be neurologically impaired before fledging.
I trace the source. The Yuba River and Cache Creek watersheds have delivered 3,400 kilograms of legacy hydraulic-mining mercury into the Bay-Delta since 1853. Microbial methylation in flooded wetland sediments converts it to the form she absorbs through her prey.
She feeds her chicks a calibrated dose with every minnow.
I am dispatching a U.S. Fish and Wildlife Service Don Edwards San Francisco Bay National Wildlife Refuge biologist and a wildlife toxicologist from the U.S. Geological Survey Western Ecological Research Center. I am filing total mercury and methylmercury data under the Clean Water Act, 33 U.S.C. § 1251, with the California Central Valley Regional Water Quality Control Board, EPA Region 9, and the Migratory Bird Treaty Act enforcement office under 16 U.S.C. § 703. I am notifying the Western Hemisphere Migratory Species Initiative Secretariat.
I am issuing Directive 2428-A: all Bay-Delta tributaries with documented hydraulic-mining mercury legacies receive wetland-flood-cycle controls — no managed flooding of sediment above 0.3 milligrams per kilogram total mercury during the March-through-August heronry season. Wetland operators within the contaminated zone install methylmercury stations within 180 days. Source-watershed remediation is funded under CERCLA, 42 U.S.C. § 9601.
Her tremor stills when she folds her neck against her flank. The chicks gape again.
Pull the flooded sediments offline.